Af­ter re­peated food poi­son­ing out­breaks linked to ro­maine let­tuce, the pro­duce in­dus­try is con­fronting the fail­ure of its own safety mea­sures in pre­vent­ing con­tam­i­na­tions.

The E. coli out­break an­nounced just be­fore Thanks­giv­ing fol­lows one in the spring that sick­ened more than 200 peo­ple and killed five, and an­other last year that sick­ened 25 and killed one. No deaths have been re­ported in the lat­est out­break, but the dozens of ill­nesses high­light the chal­lenge of elim­i­nat­ing risk for vegeta­bles grown in open fields and eaten raw, the role of nearby cat­tle op­er­a­tions that pro­duce huge vol­umes of ma­nure and the de­lay of stricter fed­eral food safety reg­u­la­tions.

A con­tested as­pect of the reg­u­la­tion, for ex­am­ple, would re­quire test­ing ir­ri­ga­tion wa­ter for E. coli.

The Food and Drug Ad­min­is­tra­tion put the mea­sure on hold when the pro­duce in­dus­try said such tests wouldn’t nec­es­sar­ily help pre­vent out­breaks. Ad­di­tional reg­u­la­tions on san­i­ta­tion for work­ers and equip­ment — other po­ten­tial sources of con­tam­i­na­tion — only re­cently started be­ing im­ple­mented.

FDA Com­mis­sioner

Scott Got­tlieb said he thinks the com­bi­na­tion of rules, once fully in place, will make vegeta­bles safer to eat.

“I don’t think any one el­e­ment of this is go­ing to be the magic bul­let,” Got- tlieb said.

Health of­fi­cials say im­proved de­tec­tion may make out­breaks seem more fre­quent. Still, that is in­ten­si­fy­ing pres­sure on grow­ers and reg­u­la­tors to pre­vent, catch and con­tain con­tam­i­na­tion.

PRE­VEN­TION

It’s not yet known how ro­maine got con­tam­i­nated in the lat­est out­break.

The spring out­break was traced to ro­maine from Yuma, Ari­zona. Ir­ri­ga­tion wa­ter tainted with ma­nure was iden­ti­fied as a likely cul­prit, and in­ves­ti­ga­tors noted the pres­ence of a large an­i­mal feed­ing op­er­a­tion nearby.

Sub­se­quently, an in­dus­try agree­ment in Ari­zona and Cal­i­for­nia was ad­justed to ex­pand buf­fer zones be­tween veg­etable fields and live­stock. The in­dus­try says the change was in place for let­tuce now be­ing grown in Yuma, which hasn’t been im­pli­cated in the lat­est out­break. But Trevor Sus­low of the Pro­duce Mar­ket­ing As­so­ci­a­tion said there isn’t con­sen­sus about the ex­act dis­tances that might ef­fec­tively pre­vent con­tam­i­na­tion.

He noted spe­cific buf­fer zones aren’t re­quired by the new fed­eral rules on pro­duce safety.

“They look to the in­dus­try to de­ter­mine what is the ap­pro­pri­ate dis­tance,” Sus­low said.

Grow­ers in Yuma also started treat­ing ir­ri­ga­tion wa­ter that would touch plant leaves with chlo­rine to kill po­ten­tial con­tam­i­nants, Sus­low said. But he said such treat­ment raises con­cerns about soil and hu­man health.

Mean­while, the prox­im­ity of pro­duce fields to cat­tle op­er­a­tions is likely to con­tinue pos­ing a prob­lem. Travis Forgues of the milk pro­ducer Or­ganic Val­ley noted con­sol­i­da­tion in the dairy in­dus­try is lead­ing to big­ger live­stock op­er­a­tions that pro­duce mas­sive vol­umes of ma­nure.

But James Rogers, di­rec­tor of food safety re­search at Con­sumer Re­ports, said it’s im­por­tant to make wa­ter test­ing a fed­eral re­quire­ment. Since ro­maine is of­ten chopped up and bagged, a sin­gle con­tam­i­nated batch from one farm that skips test­ing could make a lot of peo­ple sick, he said.

Ter­essa Lopez of the Ari­zona Leafy Greens Mar­ket­ing Agree­ment also said fed­eral reg­u­la­tion can en­sure greater com­pli­ance, even though the in­dus­try agree­ment has stricter mea­sures.

De­spite in­dus­try mea­sures im­ple­mented af­ter a spinach out­break more than a decade ago, health of­fi­cials noted this month there have been 28 E. coli out­breaks linked to leafy greens since 2009.

The pro­duce in­dus­try says the fail­ure to pre­vent the Yuma out­break could also re­flect the lim­i­ta­tions of test­ing wa­ter for generic E. coli.

El­iz­a­beth Binh, a food science ex­pert at Cor­nell Uni­ver­sity, said the tests look for the amount of fe­cal mat­ter in wa­ter. The prob­lem is, “some fe­ces has pathogens in it, some fe­ces doesn’t,” said Binh, who is part of a fed­eral pro­gram help­ing farm­ers com­ply with the new pro­duce reg­u­la­tions.

Test­ing for spe­cific E. coli strains that are harm­ful is more dif­fi­cult, and it doesn’t rule out the pos­si­bil­ity of other harm­ful bac­te­ria, Binh said.

CON­TAIN­ING

Whole-genome se­quenc­ing is mak­ing it eas­ier to de­tect out­breaks, which is pres­sur­ing the pro­duce in­dus­try.

The FDA warned against all ro­maine last week be­cause it said it was able to iden­tify it as a likely source early enough. The agency nar­rowed its warn­ing to ro­maine from Cal­i­for­nia’s Cen­tral Coast af­ter the pro­duce in­dus­try agreed to la­bel ro­maine with har­vest dates and re­gions, so peo­ple know what’s OK to eat.

The la­bel­ing is vol­un­tary, and the in­dus­try said it will eval­u­ate whether to ex­tend it to other leafy greens. Got­tlieb said im­prov­ing trace­abil­ity would al­low tar­geted health alerts that don’t hurt the en­tire in­dus­try. The FDA re­cently hired a for­mer Wal­mart ex­ec­u­tive who used blockchain tech­nol­ogy to im­prove trace­abil­ity in the re­tailer’s sup­ply chain.

Stephen Ba­sore, di­rec­tor of food safety at a Florida ro­maine grower, said he ex­pects more reg­u­la­tions and self-im­posed in­dus­try guide­lines.

“Any­time there is an is­sue, the im­me­di­ate re­sponse is say­ing our pro­to­cols aren’t enough,” he said.

MARK J. TERRILL AP

Ro­maine let­tuce sits on the shelves in the pro­duce sec­tion of a su­per­mar­ket late last month in Simi Val­ley, Cal­i­for­nia. Health of­fi­cials say im­proved de­tec­tion may make out­breaks seem more fre­quent, but pres­sure on grow­ers and reg­u­la­tors is in­ten­si­fy­ing to pre­vent, catch and con­tain con­tam­i­nated prod­ucts.